Fix mihawk fan event build error

Now the mihawk fan event will build error on openbmc master.
So I made some changes in order to solve the problem.

Tested: Verify fan control functionality of mihawk image

Signed-off-by: Ben Pai <Ben_Pai@wistron.com>
Change-Id: I9f525f27f5fb7161de9f8c1cee40b54efb65bf4d
1 file changed